Maximizing Edge Retention – What CATRA Reveals about the Optimum Edge

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Wow what a great article! Every one of your articles has been excellent, but this one is my favourite
 
Nice write up but I am going to have to re-read it after work. Too much for my brain over coffee.
 
Another great article. I'm surprised about the effect (or lack thereof) of sharpening angle. Maybe I missed it/misunderstood in the article, but any comment on how the 20 and 34 degree angles produced alternating cut lengths (ie long, short, long) from cut to cut after they lost about 50% of cut length? Wouldn't one expect that there would be a steady decline? It appears almost like the shorter cuts are stropping the edge to produce a longer cut on the next attempt.
 
Another great article. I'm surprised about the effect (or lack thereof) of sharpening angle. Maybe I missed it/misunderstood in the article, but any comment on how the 20 and 34 degree angles produced alternating cut lengths (ie long, short, long) from cut to cut after they lost about 50% of cut length? Wouldn't one expect that there would be a steady decline? It appears almost like the shorter cuts are stropping the edge to produce a longer cut on the next attempt.
I don't know the answer to that. I know if you watch the test you see that the cuts are not always continuous due to resetting the card stack. Perhaps that has something to do with it. I'm not sure what you mean by the lack of effect of sharpening angle since that was the strongest effect described in the article.
 
I don't know the answer to that. I know if you watch the test you see that the cuts are not always continuous due to resetting the card stack. Perhaps that has something to do with it. I'm not sure what you mean by the lack of effect of sharpening angle since that was the strongest effect described in the article.

Regarding sharpening angle, sorry I wasn't clear. I was referring to the notion that a more obtuse angle will retain the edge better than an acute one. In these experimental conditions, this was not the case, and the acute edge still offered a slight advantage after 60 cuts.
 
Regarding sharpening angle, sorry I wasn't clear. I was referring to the notion that a more obtuse angle will retain the edge better than an acute one. In these experimental conditions, this was not the case, and the acute edge still offered a slight advantage after 60 cuts.
Got it. :)
 
And this only makes sense with steels that easily take and hold those acute angles. And perhaps I may suggest that in normal kitchen work the board contact is a more decisive factor in edge retention than the produce.
Thanks a lot for sharing!
 
And this only makes sense with steels that easily take and hold those acute angles. And perhaps I may suggest that in normal kitchen work the board contact is a more decisive factor in edge retention than the produce.
Thanks a lot for sharing!
As you may know, the property of a steel to be able to handle acute edges is called "edge stability." I think it is better to evaluate it independently when it comes to comparing the behavior of the edge. Because different users, different knives, different types of cutting, and different materials being cut will lead to different "composite behavior" when combining resistance to rolling, chipping, and wear. The CATRA test focuses almost entirely on wear.
 
IIRC Wüsthof has used CATRA results in advertising. But wear resistance isn't all that relevant in the kitchen, or am I missing something?
 
IIRC Wüsthof has used CATRA results in advertising. But wear resistance isn't all that relevant in the kitchen, or am I missing something?
That depends. Are your edges blunting due to rolling, chipping, corrosion, or wear?
 
You would probably be able to see chipping, rolling, or corrosion with a handheld microscope.
 
Does this mean that for maximum edge retention (at least against silica impregnated card), a blade should be sharpened to the most acute angle that it will tolerate without generating carbide pull-out (or edge rolling for a softer knife)? Or do we not have enough information about that from this experiment?
 
Does this mean that for maximum edge retention (at least against silica impregnated card), a blade should be sharpened to the most acute angle that it will tolerate without generating carbide pull-out (or edge rolling for a softer knife)? Or do we not have enough information about that from this experiment?
Yes, the edge should be as acute as possible while avoiding chipping and/or rolling.
 
That raises an intersting question,
how does acid + wear resistance
play out in the real world?

154 variants are already some
degree of stainless,

but maybe in general does
high wear rating help
vs acids ?

Or, are the two variables
not usefully correlated?
 
The only thing that helps against corrosion is corrosion resistance. There is some literature out there on combined corrosion and wear but I’m not sure if there are any on blades.
 
Makes sense,
thanks for the explanation.
 
Wouldn't BESS style measurements taken after testing repeated *impact* on wood layered with some substance of edible texture be far more relevant than cardboard cutting....?


...


How long does the edge on the cheapest kind of yanagiba (420J2 steel) last, once decently sharpened? ... Longer than one would think, if only used as a strict pull cutter....
 
For people who are just skimming the thread, this pic is from the article.
Very well done writeup, so encourage people to click thru,

>http://knifesteelnerds.com/2018/06/18/maximizing-edge-retention/

Relative-contribution-to-edge-retention.jpg
 
Wow this was a really interesting article. THanks for the read. Learned a lot and well presented. Will inform my future purchases/sharpening!
 
can someone give me the cliff notes version (laymans summary)?

I'm a knife scrub but decent with data usually, so either this is highly appropriate or highly inappropriate to answer :p

The shallower the angle of the knife tested until 20 degrees (10 a side) on the type of steel they used correlated very strongly with ability to cut better over time.

However the biggest drop in cutting ability happens very quickly and similarly across knives, the original advantage of the 20 degree knife is eroded over time, but stays sharper longer.

Hardness, edge thickness, hardening technique (cyro, yes or no), and grit of final stone used all correlated with edge retention SLIGHTLY, no where near the magnitude of the angel sharpened too.

EDIT: Cliff of CLiff: So sharpen your knives well to the finest edge you can wo rolling/damaging profile of the edge (im assuming this is some sort of given, sharpen well...). It will cut better longer, this was tested between 20 and 60 degrees
 
so this scientifically just confirmed what we already knew?

With a very large degree of magnitude :plus1:

That said I actually didn't know this, I had heard a bunch of myth about thicker edge maybe lasting longer. And it puts a contrast on HOW correlated it is. This correlation dwarfs all others listed.

So buying a high HRC blade is good because you CAN sharpen it to a finer edge. Just having a harder blade won't make the edge last longer (well it will, but this improvement is absolutely dwarfed by edge angle) - so if you don't want to sharpen or can't better than, 40 degrees for whatever reason theres no purpose to a higher HRC blade
 
Sounds like a guideline for those who favor edge stability. But for those that favor edge retention...well that’s another can of beans...no? I probably shouldn’t even comment yet as I haven’t read the actual article.
 
Sounds like a guideline for those who favor edge stability. But for those that favor edge retention...well that’s another can of beans...no? I probably shouldn’t even comment yet as I haven’t read the actual article.

The data looked like it showed that over more cute the lower angled knives always cut better than the knife on a similar number of cuts sharpened to a different angle. Initial advantage is never overcome by some other property...but I also would really like to know if I am misreading this horribly wrong, as, again, scrub

"There was a difference in final thickness of the apex of the edge after the knives were run through the CATRA test. The 20° edge was about 23 microns after the test, 34 degrees led to about 19-20 microns, and the 50° were around 16-17 microns. All of these images are of the ingot 154CM steel. So it appears that with a lower angle edge it can wear down to a larger apex and still maintain better sharpness than a higher angle edge."
 
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